DESCRIPTION (Applicant's Abstract): The complex and dynamic nature of the HIV epidemic has demanded that CAPS research feature an array of sophisticated study designs, specialized quantitative (both behavioral and biomedical), and qualitative measurements, and complex clustered or longitudinal data. In addition, increasing numbers of studies involve multiple sites, depend on multiple modes of data acquisition, and require rapid implementation. Given this complexity, it is understandable that few investigators are fully knowledgeable about the multitude of methodologic issues presented by each study. A centralized resource for methodologic expertise is likely the most cost-effective approach to serve the needs of CAPS scientists in their mission to respond expeditiously to the changing HIV epidemic in the most scientifically rigorous fashion. Therefore, we propose to form a new core for CAPS, a Methods Core, whose objective is to provide project-specific consultation, peer review, and center-wide education in quantitative and qualitative research methods and methods of data acquisition and data management. In addition, the Methods Core will serve as the catalyst for methodologic research at CAPS. Specifically, the core will provide expertise in: 1. Quantitative methods for HIV related research including: a) Design of both observational and experimental studies; b) Optimal selection of quantitative behavioral and biomedical measurements; and c) Analysis of both observational and experimental data. 2. Qualitative methods pertaining to HIV related research including: a) Design of focus groups, one-on-one interviews, and participant-observation studies; b) Systematic collection of qualitative data; and c) Theory building via inductive analysis including interpretive strategies and theory triangulation. 3. Methods for state-of-the-art data acquisition and data management including: a) Instrument and database creation; b) Data entry, verification, and validation; and c) Report generation and maintenance of data security.